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(N0 lfiohel. 3 Sheets Sheet 1. O. D. ROGERS. DIE FOR ROLLINGSGREW'THREADS.

Patented Oct. 20, .1891.

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(No Model.)

\ Patented Oct. 20,1891.

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Patented 00h 20,-;1891.

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3,, fiiwiw t WW M- j M a A -wfi UNITED STATES PATENT OFFICE.

CHARLES D. ROGERS, OF PROVIDENCE, RI-IODE ISLAND, ASSIGNOR TO THEAMERICAN SCREIV COMPANY, OF SAME PLACE.

DIE FOR ROLLING SCREW-THREADS.

SPECIFICATION forming part of Letters Patent No. 461,620, dated October20, 1891.

Application filed March 10, 1891. Serial No. 384,517. (No model.)

To ctZZ whom it may concern.-

Be it known that I, CHARLES D. ROGERS, a citizen of the United States,residing at Providence, in the county of Providence and State of RhodeIsland, have invented certain new and usefulImprovernents in DiesforRoll.- ing Screw-Threads; and I do hereby declare the following to be afull, clear, and exact description of the invention, such as will enableto others skilled in the art to which it appertains to make and use thesame, reference being had to the accompanying drawings, and to lettersof reference marked thereonfivhich form a part of this specification.

My invention has relation to dies such as are mployed in forging (cold)the screwthreads upon screws by what is termed the rolling process, theclass of screws to which the invention more especially appertains beingknown as wood-screws. Rolled woodscrews, even though made of the samewire, vary greatly in their holding-power according to the form or shapeand inclination of the ribs and grooves of the thread-forming dies. Theform of the ribs of such dies transversely as first employed inthread-swaging was, I believe, V-shaped, the shape and area of each ribbeing uniform throughout its length. The action of such dies upon ascrew- 0 blank is to elongate it, the diameter of the threaded portionbeing the same as that of the wire itself or unthreadedpart. I wouldstate that the die just referred to was employed to produce the threadson small ma- 3 5 chine-screws having fine pitchsuch, for example, as areused to secure the knobs or handles to the spindles of door-latches. Alater example of thread-rolling machines and dies is that shown in apatent of the United States, granted to Clarke and Harvey, October 7,1884, No. 306,132. In that patent the ribs of the dies cross-sectionallyare V-shaped at the commencement or entering end, but are graduallytransformed into a truncated 5 shape. In operation the ribs aregradually forced into the screw-blank axially from the commencement tothe end, thereby producing a groove which is gradually deepened andwidened, the metal being forced outwardly from under the ribs of thetraveling dies in the form of ridges or threads which gradually increasein diameter. In that die the angle or inclination of the sides of theribs varies throughout its length-that is to say, the included angleformed by the sides of adjacent ribs at the entering end of the die ismuch greater than that at the opposite end. Consequently its actionuponthe metal isirregular. The screw is both enlarged laterally andlongitudinally during the thread-forming oper- 6o ation. There are stillother forms of dies adapted to swaging screw-threads. I have inventedone wherein the inclined ribs and also the grooves thereof transverselyare uniform in shape and area throughout. Such dies, however, cannotwell produce screws having the threads raised above the normal surfaceof the blank to the extent necessary or essential to Wood-screws adaptedto be inserted into wood by a screw-driver. Therefore I employ 7c thedies in making what are termed drivescrews that is, screws havingmultiple threads and coarse pitch. Screws of this class and as made bymy said dies are readily driven into wood by the blows of a hammer andturn axially While being driven.

In United States Patent No. 370,354, granted to me September 20, 1887, Ihave shown and described dies for forming the threads upon wood-screwsby rollingthe blanks between them and raising the metal to form thethread radially from the body of the blank without extending the blanklengthwise. In using 5 the dies the pressure upon the metal toward theaxis of the blank is limited to the commencement of the rollingoperation and to a comparatively small part of the metal displaced. Thework of raising the threads is mainly performed by the inclination ofthe adjacent or lateral sides of the ribs, such in- 0 clination beingconstant from one end of the die to the other. The face of the ribs atthe entering end, where the rolling commences, is quite'narrow, in orderthat they may be re quired to displace but little metal. The ribs 5gradually increase in thickness laterally from the commencement to theend of the die, the faces thereof being flattened or truncatedthroughout. A pair of these dies in operation produces agradually-developed screw-thread, because at each successive revolutionof the blank the metal lying between the constantlyvarying (inthickness) ribs is more and more compressed laterally and at the sametime gradually expanded radiallyinto the grooves of the dies until atthe end of the operation it fills them and the thread is completed. The

thread cross-sectionally is solid and wedgeshaped, being quite thin atits base or root where it joins the core and sharp at the point or edge.In these screws, the bottom of the groove being parallel for its wholewidth with the axis of the screw, the top of the ribs must be flat andthe metal of the blank at the bottom of the groove must be displaced bythe ribs of the die to the full width of the groove by a kind ofshearing action at the bottom of the groove.

The present invention is an improvement of the above-mentioned die andis designed to act by a lateral pressure of the metal of the screw-blankand its radial expansion, as with the dies just referred to, but by aneasier displacement of the metal, with less or none of the shearingaction at the bottom of the groove of the screw, as above explained, inthe use of fiat-faced ribs. I accomplish this object by roundingtransversely the top of the ribs of a die for a part or the whole oftheir length. The eflfect of this is to reduce the width of the inclinedsides of the ribs, which act upon the metal laterally as the thicknessof the ribs transversely increases, and to leave a portion of the metalundisturbed, which would be displaced to form the angle at the bottom byflat-faced ribs, and a groove rounded at the bottom is produced insteadof a flat-bottomed groove, forming an angle with the sides of thethreads or ribs of a screw.

In the annexed three sheets of drawings illustratingmypresentimprovements, Figure 1, Sheet 1, represents a plan of theworking face of one die. The lightly-shaded parts indicate the faces ofthe ribs. Fig. 2 is a longitudinal sectional view taken, say, on line mm of Fig. 1, showing the ribs constantly decreasing in height. Fig. 3 isa similar sectional view, the height of the ribs being constantthroughout. Fig. 4 is a transverse sectional View taken through a pairof the dies at or near the finished end, showinga screw in partialsection between them. Fig. 5 is a plan view of one of the ribs of thedie detached, one portion of the ribs face being flat or truncated, theother being rounded, as indicated by the shade lines. Fig. 6 is asimilar view of a rib, its face being rounded throughout its length.Figs. 7, 8, and 9 are cross-sectional views of the rib, taken,respectively, on lines a: at, w w, and o o of Fig. 5. Fig. 10 is atransverse sectional view taken on line 00 a: of Fig. 6. Figs. 11 and 12are similar sectional views showing modified forms of the ribs. Fig. 13,Sheet 2, is a longitudinal sectional view showing my improved die bentto a circle or curved in lieu of being straight. Figs. 1a and 15 aretransverse sectional views showing the form of die-ribs as patented toHarvey, before referred. to. Fig.

16 is a plan view of one of the last-named ribs provided with a roundedface. Figs. 17 and 18 are cross-sectional views thereof, taken,respectively, on lines a; a: and o o of Fig. 16. Fig. 19 is alongitudinalsectional view, enlarged, taken through the center of agimletpointed wood-screw provided with my improvement. Fig. 20 isasimilar view of the screw having a double-thread and unthreadedspur-point. Fig. 21, Sheet 3, is a plan view of the working face of adie embodying my improvement. The shaded portions indicate the ribshaving rounded faces, the general arrangement of the ribs being in theform of steps, or terraced, substantially as represented in UnitedStates Patent No. 441L329, granted to me November 11, 1890. Fi s. 22,23, 24, and 25 are cross-sectional views taken, respectively, on lines aa, b b, c c, and at (Z of Fig. 21. Fig. 26 is a plan view of a ribenlarged, having a uniform width and shape throughout its length; andFig. 27 is a transverse sectional view taken on line 6 c of Fig. 26,showing the relation of adjacent ribs to each other.

A in the several figures indicates my improved die as a .whole. The ribsof the die are designated by a an d the grooves or spaces lying betweenthem by b. The grooves and ribs at the commencement or entering end ofthe die are substantially V-shaped, the angle or inclination of theadjacent sides of the grooves being practically constant from one end ofthe die to the other, as represented in Sheet 1 of the drawings. Theheight of each rib a may vary throughout, as indicated by Fig. 2, orthey may be uniform in height, as in Fig. 3. In any case the width ofthe face of the rib varies, being narrowest at the entering end of thedie and widest at the opposite or finishing end. Such width of ribs mayvary constantly and gradually, as shown in Fig. 1, or they may be in theform of a series of increasing steps, as c c c c, Fig. 21.. The face ofthe rib at the entering end should be made as thin or narrow as isconsistent with the work imposed upon it. The face thereof for a portionof its length may be flat or truncated, as at to, Figs. 5 and 7, suchfiat portion being joined to a gradually-increasing rounded part, (seeFig. 5,) the latter part terminating in well-rounded ribs, as clearlyindicated by Fig. 9, which represents, enlarged, a partial cross-sectiontaken on line in a: of Fig. 1 and also on line '0 0 ofFigs. 5 and o. Theface of the ribs 0. may be rounded throughout, as shown by Fig. 6, andits sections as cc, to w, and o 0 represented by Figs. 10, 8, and 9,respectively. Obviously the shape of the grooves b gradually changesfrom the V form at the front end, Figs. 7 and it), to the opposite orfinishing end of the die, where the grooves diverge laterally in curvedsides, Figs. 4 and 9, which are the counterpart of the sides of thescrew-threads t. (See also Figs. 18 and 25.)

In the (llarke and Harvey die before referred to, the oblique ribs andgrooves are uniform in height throughout the length of the die; but theangle or inclination of the sides thereof constantly varies, asindicated by Figs. 14 and 15. The former figure shows enlarged,cross-sectionally, a portion of the die at the entering end and thelatter a similar figure taken at the opposite or finishing end. The riba is V-shaped at the front, its face being sharp and gradually wideningtherefrom to the other end, (see a Fig. 15,) thereby gradually changingthe angle of its sides until a sharp V-shaped groove 12' is produced,Fig. 15, which is a counterpart of the thread. The ribs and grooves ofsuch a die may be rounded, as indicated by Figs. 16,17,

and 18, the latter then representing ribs to and grooves 19,substantially like those shown by Figs. 4, 9, and 25. Although dieshaving ribs and grooves, as shown by said Figs. 16, 17, and 18, may beemployed to swage or roll the threads of screws, I preferably use dieshaving the angle or inclination of the sides of the ribs a substantiallyconstant from one end of, the die to the other, Figs. 1 to 10, becausethe threads thus produced are more gradu ally developed and morehomogeneous, the percentage of loss is less, and the work isaccomplished with less power.

The die A may be secured to a revolving cylinder or carrier m, Fig. 13,the operation of rolling the screws then (if combined with a stationarydie) being substantially as set forth in the Patent No. 306,132, grantedto the said Clarke and Harvey by the United States, hereinbeforereferred to.

In Figs. 11 and 12 the bottom of the ribs a are rounded as well as thefaces. The last or finishing section, however, would be substantially asrepresented by Fig. 9. An advantage resulting from thus filleting theroot of the ribs for a portion of their length is that it increasestheir strength in a lateral direction.

A die provided with ribs a Figs. 26 and 27,

'having a uniform width and area transversely throughout their length,may be employed; but the ribs cannot produce a gradually-de velopedscrew-thread as compared with my improved die provided with developingribs a, because the grooves b Fig. 27, themselves are uniformthroughout.

3 indicates my improved wood-screw, the threads t thereof being producedby rolling by means of the dies A, hereinbefore described. The shank orunthreaded portion 8 of the screws I make slightly tapering orconical.This is performed in the dies simultaneously with the operation ofupsetting the metal therein to form the heads 72.. Practically I preferthat the diameter of the shank at its intersection with the head shallbe substantially the same as the diameter of the threaded portion. Thethreads t are filleted at the bottom 25, thus adding to their strengthin a-lateral direction. The screws may be gimletpointed, as at 19, Fig.19, or the point-thread may be wholly or in part omitted, therebyproducing a spur-point 19, Fig. 20.

The ribs to and grooves b ofmy improved die A may be cut by a revolvingmilling-tool or a series of them, having the proper form to give therequired inclination or bevel to the sides of the ribs. The die-blank isfirst elevated at one end and secured to a reciprocating table orcarriage in such manner that its longitudinal axis in a horizontal planeis not parallel with that of the moving table, which latter carries theblank past and in contact with the tool. The rounded form given to theface of the ribs may be done simultaneously with the cutting of thegrooves; but practically I prefer to first truncate them by the tooljust referred to, after which the ribs faces are rounded off by anothercutter or cutters or by other suitable means. The dies are subsequentlyhardened, thereby rendering them ready for use.

The action of the dies in forming the filleted threads t t of a screwmay be described as follows: Let it be assumed that a pair of the diesA, with the ends reversed, are arranged to move back and forth past eachother in a suitable machine, or substantially as shown and set forth inUnited States Patent No. 389,168, granted to me September 4, 1888. Toroll a screw the blank is introduced vertically between the ends of theseparated dies, (the latter then being at the end of the stroke or onthe dead-center,) which immediately seize it from opposite sides. Theblank is rolled axially by the action of the two traveling dies untilthey pass each other, when it drops from them completely threaded. Atthe commencement of the operation the narrow ends it of the ribs a ofthe dies are forced into the metal to the maximum depth required, thelateral separation of the working faces of the oppositedies beingconstant throughout and corresponding to the diameter of the root orcore of the screw. As the rolling progresses the metal seized betweenIIO each pair of the ribs above the curved portion of the ribs iscompressed and at the same time gradually expanded into the groove Z) ofthe dies, until at the end of the operation it fills them and the thread2525' is completed, the threaded portion then being substantially asrepresented by Figs. 4, 19, and 20.

I claim as my invention 1. A die for raising the threads of a. rolledscrew radially from a screw-blank by compressing the metal for thethread laterally between the converging sides of the ribs of the die andhaving the faces of the'ribs rounded to form a concave bottom of thegrooves of a screw, said ribs being narrow at the end where theycommence to form the thread, so that they may be forced at thecommencement of their action into the metal to the depth required toform the body of the screw, and increasing in width act laterally uponthe metal between the ribs and force it into the grooves, Which at theend of the operation give it the precise form required for the thread.

2. The die A, substantially as hereinbefore described, for raising thethreads of a rolled screw radially from a screwblank, the work ing,surface of the die being provided with a series of obliquely-arrangedexpanding or developing ribs to, having rounded faces and I0 convergingadjacent sides, each rib being narrow at the end where it commences toform the thread and increasing in Width transversely to the opposite endof the die.

In testimony whereof I have affixed my signature in presence of twowitnesses.

CHARLES I). ROGERS. \Vitnesses:

CHARLES IIANNIGAN, GEO. H. REMINGTON.

